In the related art, a medical instrument called an introducer has been used for introducing a catheter into a body lumen. The introducer is configured to include an introducer sheath provided with a hollow tube body generally called a sheath tube and a hub provided in the tube body, and a dilator used by being assembled with the introducer sheath.
The tube body of the introducer sheath is percutaneously introduced into the body lumen (for example, a blood vessel) from a distal side. A hollow portion (lumen) formed inside the tube body is used as an access passage that communicates with the inside and the outside of the living body. Regarding a use of the introducer sheath, it is preferable that the tube body has a large inner diameter and small outer diameter, that is, has a thickness to the smallest extent. The tube body is formed to have a large inner diameter, thereby making it possible to secure a large cross-sectional area of the hollow portion. Therefore, an instrument such as a catheter can be smoothly introduced through the hollow portion, and an instrument such as a catheter can cope with having a large outer diameter. On the other hand, the tube body is formed to have a small outer diameter, thereby having insertion resistance into the body lumen. Therefore, insertion properties into the body lumen improve, and further a minimally invasive procedure can be realized because a small puncture is formed in a puncture site.
However, when the thickness of the tube body is formed to be thin to some extent, the tube body has a decrease in rigidity against bending of the tube body. Therefore, the tube body is likely to kink. In a procedure in which the introducer is used, the distal side of the tube body of the introducer sheath indwells in a puncture site, and then an instrument such as a catheter is introduced into the body lumen via the hub. Therefore, when the medical instrument is introduced into the hollow portion of the tube body, the tube body needs to have kink resistance such that the tube body does not kink on the proximal side. For example, International Publication No. WO2014/119527 proposes an introducer sheath having a configuration in which, even though a tube body kinks, a kinked portion of the tube body can be restored to the extent that an inner diameter is the same as an original diameter when pressure applied to the tube body from outside is canceled.